Endoscopic and laparoscopic surgical instruments are often preferred over traditional open surgical devices since the use of natural orifices (endoscopic) or smaller incisions (laparoscopic) tends to reduce the post-operative recovery time and complications. Consequently, significant development has gone into a range of endoscopic and laparoscopic surgical instruments that are suitable for precise placement of a distal end effector at a desired surgical site. These distal end effectors engage the tissue in a number of ways to achieve a diagnostic or therapeutic effect (e.g., endocutter, grasper, cutter, staplers, clip applier, access device, drug/gene therapy delivery device, and energy device using ultrasound, RF, laser, etc.).
Typically, endoscopic and laparoscopic surgical staplers have a stapling mechanism, the end effector, which is adapted to fit through a cannula to position the end effector relative to tissue to be stapled. The end effector has a cartridge arm containing a cartridge with staples, and an anvil that is pivotally connected to the cartridge arm. The cartridge arm and anvil each act as a separate jaw to close and hold together the tissue to be stapled. Upon cartridge actuation, staples are driven from the cartridge arm, through the tissue, and against staple-forming grooves formed in the anvil and aligned with the staples of the cartridge arm, thus forming the staples that hold the tissue together.
When a stapler simultaneously fires multiple staples in a linear arrangement, deflection of the anvil can occur. In particular, the force required to drive the staples along with relatively long unsupported length of the anvil can create substantial torque at the anvil's distal end, resulting in deflection. This can result in malformed staples, especially toward the distal end of relatively long end effectors. Since endoscopic or laparoscopic procedures utilize small orifices or access ports, the thickness or outer diameter of the end effector is necessarily limited. Even with the use of very stiff materials for the anvil (e.g., steel or titanium), deflection is still noticeable upon stapler actuation.
Accordingly, a need exists for improved devices and methods for stapling and/or cutting tissue.